As the consumer electronics industry continues to mature, and the capabilities of processors increase, more devices have become available for public use that allow the transfer of data between devices and more applications have become available that operate based on their transferred data. Of particular note are the Internet and local area networks (LANs). These two innovations allow multiple users and multiple devices to communicate and exchange data between different devices and device types. With the advent of these devices and capabilities, users (both business and residential) increasingly desire to transmit data from mobile locations.
The first widespread deployment of a protocol to deal with these issues, was Internet Protocol version 4 (IPv4) in the early 1980's. IPv4 is a network layer protocol used to provide unique addressing to ensure that two computers communicating over the Internet can uniquely identify each other. IPv4 has a 32-bit addressing scheme which allows for 232 (approximately 4.2 billion) potentially unique addresses. This limit of 232 addresses is becoming a bottleneck as the need for more unique addresses will arrive in the foreseeable future. Additionally, IPv4 was not specifically designed to be efficient for mobile users. In fact, when IPv4 was implemented there were not a lot of mobile consumer devices that could communicate across the Internet as there are today. In this context, mobile IP equipment can be considered to be any a piece of equipment that is moveable, e.g., a laptop computer, cell phone or a Personal Digital Assistant (PDA), and that crosses boundaries between different networks while desiring to maintain connectivity or be allowed to connect to a foreign network. Accordingly, as this need and the need for more IP addresses developed, Internet Protocol version 6 (IPv6) was created and is now being implemented.
IPv6 uses a 128-bit addressing scheme which allows for 2128 unique addresses, i.e., significantly more addresses than are provided for in IPv4. The addressing scheme in IPv6 is composed of two parts: a 64-bit host part and a 64-bit sub network prefix (subnet prefix). IPv6 is also more mobile friendly than IPv4, particularly with the addition of Mobile IPv6 (MIPv6).
MIPv6 uses a return routablity (RR) procedure for communications between a Mobile Network (or node) (MN) and a Correspondent Node (CN). This RR procedure generates a shared secret between the MN and the CN in order to authenticate binding update (BU) messages. Return routability involves exchanging four signaling messages between the MN and the CN. These messages allow the CN to test the MN's reachability for the MN's two addresses, i.e., the MN's IPv6 home address and the MN's foreign address. A MN's foreign address is related to the access router (AR) through which the MN is attaching to a network.
One downside of the RR process is that the four messages used to perform reachability testing put a large load on the MN with respect to both latency and battery consumption, which can negatively effect both real time use during handoffs and battery life of a mobile device. In an effort to improve MIPv6, Optimized MIPv6 (OMIPv6) allows for a reduction in the required connectivity traffic between a MN and a CN. More specifically, by removing the reachability test of the home address, systems capable of using OMIPv6 do not require two of the four messages used in MIPv6. An illustration of the required reachability test messages used in OMIPv6 is shown in FIG. 1(a). The reachability test under OMIPv6 uses two messages: a Care of Test Init (CoTI) message 102 and a Care of Test (CoT) message 104. The CoTI message 102 originates from MN 106 and is forwarded by AR 108 to CN 110. Upon receipt of the CoTI message 102, CN 110 creates and transmits the CoT message 104 back to MN 106. In this purely illustrative example only one AR 108 is shown, however multiple ARs (or nodes) can exist in the communication flow path between MN 106 and CN 110.
Both the CoTI message 102 and the CoT message 104 are types of Mobility Header messages. They can be differentiated by a different value in the MN Type field of the Mobility Header message and by their respective contents in the Message Data field. For the CoTI message 102, the Message Data field contains three parts as shown in FIG. 1(b). These parts are Reserved 120, Care of Init Cookie 122 and Mobility Options 124. For the CoT message 104, the Message Data field contains four parts as shown in FIG. 1(c). These parts are Care of Nonce Index 130, Care of Init Cookie 132, Care of Keygen Token 134 and Mobility Options 136. For more information regarding Mobility Header messages the interested reader is pointed to “RFC 3775—Mobility Support in IPv6” dated June 2004, the disclosure of which is incorporated here by reference.
This above described reduction in message quantity for mobility signaling in OMIPv6 as compared to earlier IP versions further improves the system, however more improvements can be made to mobility signaling which further reduce latency and increase battery life. Accordingly exemplary embodiments described below address the need for improving the efficiency of moving through different mobile networks with mobile equipment in order to, for example, reduce latency and extend battery life.